Synopsis The helicopter, a Bell 206 BIII, with the pilot and four passengers on board, was on a charter flight from Houston, British Columbia, to a ski cabin on Mount Morice, 10 miles to the south of Houston. The helicopter crashed approximately 2.5 miles to the north of its departure point. The helicopter was destroyed, and the pilot and passengers sustained fatal injuries. The Board determined that the pilot, while attempting to climb through a fog layer by using rising terrain as a visual reference, most likely lost the visual cues required for flight in visual meteorological conditions (VMC). The helicopter struck a ridge, probably while the pilot attempted to regain his visual reference with the ground. The pilot's decision to use the rising terrain as a visual reference under the existing visibility conditions was a contributing factor to this accident. 1.0 Factual Information 1.1 History of the Flight 1.1.1 The Occurrence Flight At approximately 1200 Pacific standard time (PST)1, a Westland Helicopters Inc. Bell 206 BIII helicopter (C-GRAH) was flown from its base in Houston, British Columbia. The aircraft was on a charter flight to a ski cabin on Mount Morice, approximately 10 statute miles to the south2 of Houston. The helicopter carried the pilot, four passengers, and approximately 100 pounds of baggage. The purpose of the flight was to transport the four passengers and their equipment to begin a cross-country skiing excursion in the Mount Morice area. In order to climb above the fog layer in the Houston area, the pilot intended to proceed to the northeast of Houston using the rising terrain of Mount Harry Davis as a visual reference. Once above the fog layer, the intent was to proceed to Mount Morice by following mountain peaks and ridges (refer to Figure 1). All times are PST (Coordinated Universal Time (UTC) minus 8 hours) unless otherwise stated. All compass directions are relative to true north. Magnetic variation is 24 East. Figure 1- Area of Intended Flight The flight was observed departing Houston at a low altitude and on a northeasterly track towards the rising terrain of Mount Harry Davis. The helicopter was heard in the Mount Harry Davis area flying in a northeasterly direction then in a westerly direction when the sound abruptly stopped. A few seconds thereafter, some witnesses stated that they heard the muffled noise of an impact. The helicopter collided with the terrain at latitude 5424'N and longitude 12640'W, at approximately 1215 PST, at an elevation of 2,369 feet above sea level (asl)3 (refer to Appendix A). 1.1.2 Additional Operational Information The flight was originally scheduled to depart at 0830 that morning and was to consist of two back-to-back shuttles to the Mount Morice area to transport the members of two families. Both families were to remain overnight in the Mount Morice area and ski to their vehicles which had been prepositioned at the base of the mountain. On the morning of the accident, the pilot was informed that the members of one family were unable to depart until 1630. In addition, he was informed that the members of the other family would also be delayed and would be unable to make the 0830 departure. This change of plans eventually resulted in the delay of the original 0830 flight to a 1200 departure, and a second flight scheduled for 1630. There was no evidence that the pilot was under pressure from the customers to complete the revenue flight. The pilot had previously made arrangements with some friends to fly to a fishing location on the completion of his early morning flight. About 1000 that morning, when he realized that his charter... 3 See Glossary for all abbreviations and acronyms. ...flight would be delayed, the pilot invited his friends to wait at his heliport while he completed the charter, which he estimated would take about 40 minutes. His intention was to continue with their original plan to fly the non-revenue fishing trip between the two charter flights. 1.2 Injuries to Persons 1.3 Damage to Aircraft The aircraft was destroyed by the impact. 1.4 Other Damage 1.5 Personnel Information 1.5.1 General Pilot-in-Command Age - 39 Pilot Licence - Commercial Medical Expiry Date - 1 May 94 Total Flying Hours - 2,993 Hours on Type - 1,899 Hours Last 90 Days - 58 Hours on Type Last 90 Days - 58 Hours on Duty Prior to Occurrence - 3 Hours off Duty Prior to Work Period - 16 1.5.2 Pilot's History The pilot commenced his flying career in September 1977 and obtained a commercial helicopter licence in April 1978. In the fall of 1985, he underwent fixed-wing flying training in Moncton, New Brunswick. Included in this training was 19.2 hours of instruction on instrument flying techniques. This training did not entail any training in actual instrument meteorological conditions (IMC) and was the only instrument flying training known to have been received by the pilot. The pilot had flown a variety of helicopter types and was experienced in mountain- flying operations. The majority of his flying experience was on the Bell 206 helicopter in various types of helicopter operations. Based on numerous anecdotal weather-related entries in his pilot's log-book, it is known that the pilot had considerable experience operating the helicopter under visual flight rules (VFR) and in conditions of reduced visibility. There was no evidence found, however, that the pilot habitually flew in visibilities lower than permitted in existing regulations. The pilot joined Westland Helicopters on 30 May 1993 as the base manager in Houston, British Columbia, and had flown out of that base on a regular basis since joining the company. At the time of the accident, the pilot held a valid commercial helicopter licence and held a Category 1 medical with no restrictions. The pilot was not endorsed for flight in IMC. 1.6 Aircraft Information 1.6.1 General Manufacturer - Bell Helicopter Textron Type - 206 BIII Year of Manufacture - 1981 Serial Number - 3304 Certificate of Airworthiness (Flight Permit) - Valid Total Airframe Time - 6,068.1 hours Engine Type (number of) Allison 250-C20B - (1) Propeller/Rotor Type (number of) Two-bladed/semi-rigid - (1) Maximum Allowable Take-off Weight - 3,200 pounds Recommended Fuel Type(s) - Jet B Fuel Type Used - Jet B 1.6.2 Helicopter Certification The helicopter was certified, equipped, and maintained in accordance with existing regulations and approved procedures. The helicopter was not equipped or certified for flight in instrument meteorological conditions. 1.6.3 Weight of the Helicopter at the Time of Impact According to the Bell 206 BIII flight manual, the maximum allowable helicopter weight for the flight was 3,200 pounds. The helicopter was refuelled by the pilot on the morning of the flight but no records were found regarding the amount of fuel put into the helicopter. A review of the helicopter's journey log-book revealed that the pilot commonly put on only 500 pounds of fuel prior to commencing the day's flying activity. The helicopter was equipped with a long range fuel extender which would have allowed for a maximum fuel capacity of 91 U.S. gallons. At 6.78 pounds per gallon, the maximum fuel weight which could have been on board was 616.98 pounds. The fuel consumption rate for the Bell 206 BIII helicopter is approximately 23 gallons (156 pounds) per hour. Allowing 45 minutes for the pilot's start-up and flight earlier that morning for a weather check, and assuming another 15 minutes for the accident flight, the helicopter would have burned a total of approximately 156 pounds of fuel prior to the occurrence. Given the weight of the occupants and their baggage, and assuming that the pilot had refuelled the helicopter to its maximum capacity earlier that morning, the helicopter would have been at its maximum all-up weight (AUW) at the time of the occurrence. In light of the pilot's prior refuelling habits, however, it was considered more likely that the pilot would have refuelled the helicopter to 500 pounds fuel capacity prior to the flight. In that case, at the time of the occurrence, the helicopter would have been approximately 150 pounds below its maximum AUW. 1.6.4 Bell 206 Performance at Maximum AUW The accident site was at an altitude of 2,369 feet asl. The temperature at that altitude at the time of the occurrence was determined to be approximately 0 Celsius (C). According to the helicopter manufacturer's performance charts, at the weights previously mentioned and at an outside air temperature of 0C, the helicopter was capable of hovering out of ground effect up to an altitude of approximately 6,000 feet asl. 1.7 Meteorological Information 1.7.1 General There were no Atmospheric Environment Services (AES) aviation forecasts or actual weather observations for Houston, British Columbia. The nearest aerodrome for which an aviation forecast and actual weather observations were issued was Smithers, British Columbia, 31 statute miles to the northwest of Houston. 1.7.2 Weather Conditions Known to the Pilot At 0815 on the morning of the accident, the pilot called the Flight Service Station (FSS) at Smithers to inquire about the weather conditions. The Smithers FSS specialist informed the pilot that the weather at Smithers was an indefinite 400-foot ceiling and the visibility was 5/8 of a mile in fog. In addition, the specialist informed the pilot that, due to the weather, there had been no aircraft movements into or out of Smithers and there were no reports on the thickness of the fog. The pilot informed the FSS specialist that the estimated visibility in Houston was 3/4 of a mile in fog. Later that morning, at 0915, the pilot again called the FSS at Smithers and reported that he had just completed a flight to check the weather conditions in the Houston area. He reported that the surface visibility at Houston was approximately two miles in fog and that the ceiling was approximately 300 feet obscured. He further stated that, during his flight, he was able to climb above the fog layer by flying up the rising terrain of Mount Harry Davis and using the trees as visual reference. While in the climb, he stated that he was able to see a distance of about four or five tree-top lengths (assumed to mean he could see four or five tree-tops ahead of him while flying) and that he was clear of the fog at 3,800 feet asl. He characterized these conditions as helicopter VFR. Conditions above the fog were described as clear with only high scattered cloud. 1.7.3 Aftercast by Atmospheric Environment Services A post-accident weather analysis prepared by AES determined that, on the day of the occurrence, a 1048 millibar arctic high pressure area centred over southeastern Yukon was generating a light northeasterly low level flow over central British Columbia. The air mass was stable and fairly moist in the lowest levels, but was dry aloft. Satellite imagery taken 1 1/2 hours after the accident revealed that the valley containing Houston was shrouded in fog and stratus. This stratus layer produced local ceilings of 300 to 800 feet and was topped at 3,500 feet asl. Skies were clear above this stratus layer. Fog reduced the visibility to less than 1/2 mile in some areas. The temperature in the stratus layer was near but below the freezing mark and light rime icing would occur in the cloud. Although there was a risk of freezing drizzle forecast for Smithers until 1200 PST and very light freezing drizzle was reported overnight in Smithers, it ended six hours prior to the accident and appeared to be very localized. The surface temperature and dew point at Smithers at the time of the occurrence were 0C. The low-level winds were generally from the northeast at less than 10 knots, and any turbulence would have been light. 1.7.4 Additional Weather Information Approximately 1/2 hour after the accident, a helicopter departed its Houston base to search for the missing aircraft. The pilot reported that, because of reduced visibility in thick fog, he had to hover taxi over the trees up the side of Mount Harry Davis. He reported that the visibility was 1/4 of a mile or less, and that the fog was about 1,500 feet thick. In addition, he reported having encountered a trace of airframe icing while in fog, but said that no ice had accumulated on his windscreen. 1.8 Communications There was no communication by the pilot with Air Traffic Services (ATS) nor was any required. Prior to departure, the pilot had left a hand-held radio with his friends who would be waiting for his return. The radio was tuned to 159.72 megahertz (MHz), a frequency commonly used by the local forestry industry. The pilot had successfully conducted a radio check with his friends on this frequency prior to take-off. No further transmissions by the pilot were heard on this frequency. 1.9 Flight Recorders The helicopter was not equipped with a flight data recorder or a cockpit voice recorder, nor was either required by regulation. 1.10 Witness Observations Friends of the pilot observed the helicopter depart to the northeast towards Mount Harry Davis until the helicopter was lost from view due to the fog. The elevation of the departure point was 1,903 feet asl. A witness, approximately 1/2 mile to the northeast of the helicopter's departure point, heard the helicopter proceeding overhead to the northeast. He had listened to the helicopter manoeuvring for what appeared to be approximately 30 seconds when the noise suddenly stopped. Shortly thereafter, he heard a muffled impact sound. Another witness, in her home approximately two miles to the northeast of the helicopter's departure point, heard the helicopter approaching from the southwest at low level. This witness was at the 2,500-foot level of Mount Harry Davis. She heard the helicopter proceeding northeastward up Mount Harry Davis then returning directly towards her home from the east. It was her impression that the helicopter was descending along the mountain directly towards her. The helicopter's proximity and low altitude caused her some concern until she heard the helicopter turn to a westerly direction and away from her house. At this point the helicopter was flying towards a small valley. The witness stated that the visibility in that direction from her vantage point was less than 300 feet. The witness heard the helicopter proceeding to the west until the sound abruptly stopped. Approximately three seconds later, the witness heard a muffled popping sound. Another witness, approximately 1/2 mile to the west of the preceding witness and at an elevation of approximately 2,400 feet asl, heard the helicopter overhead proceeding to the west. This witness estimated the visibility at ground level as being 150 feet in fog. All ear witnesses reported that, although they could clearly hear the helicopter, they could not see it because of the fog. 1.11 Search and Rescue Efforts The emergency locator transmitter (ELT) was destroyed in the crash. At approximately 1220, a witness who believed he had heard the sound of a helicopter accident passed this information to the individuals who were waiting at the hangar for the pilot's return. Attempts to contact the helicopter using the hand-held radio were unsuccessful. At 1245, a local helicopter departed Houston to search for the missing helicopter. The search helicopter followed the intended route of the accident helicopter up Mount Harry Davis and, once on top of cloud at an altitude of approximately 4,000 feet asl, proceeded to the ski cabin on Mount Morice. No trace of the helicopter was found. Poor visibilities due to cloud and fog precluded searching in the Houston area below an altitude of approximately 4,000 feet asl. At approximately 1405, the search helicopter returned to its hangar to await an improvement in the weather. Following this flight, the helicopter crew informed the local RCMP detachment and the Rescue Coordination Centre (RCC) in Victoria, British Columbia, of the missing helicopter. The RCMP alerted the Houston Provincial Emergency Program (PEP) ground search team, who began preparations for a ground search. RCC Victoria began preparations to launch two military search aircraft from Comox, British Columbia. As local concern for the missing helicopter mounted, various individuals, including members of the local RCMP detachment, conducted a ground search using vehicles along local logging roads with no success. At approximately 1515, after an improvement in the weather conditions, the local search helicopter departed on its second attempt to find the missing helicopter. It located the accident site at approximately 1530. 1.12 Wreckage and Impact Information 1.12.1 General The helicopter had struck the ground along a ridge line which had an upslope of 6.5 degrees. The flight path angle prior to impact was determined to be 12 degrees down relative to the horizon. The wreckage trail was oriented on a track of 181 true and was 443 feet long and 190 feet wide. At impact, the helicopter was yawed 17 degrees to the left, banked 9 degrees to the left and pitched 2 degrees nose down. Based on the wreckage scatter, its airspeed was conservatively estimated to be 100 mph and its rate of descent was determined to be in excess of 1,000 feet per minute (fpm). Although all major components of the helicopter were recovered, deep snow prevented the locating of some of the smaller pieces of the wreckage. All the wreckage that was found was removed from the accident site for further examination. The four sets of cross-country skis and poles which had been fastened to the skid gear of the helicopter were recovered at the site. 1.12.2 Instrument and Annunciator Panels The instrument panel and the annunciator panel were sent to the TSB Engineering Branch Laboratory for examination (LP 35/94). The instrument dial faces and internal drive assemblies were examined but provided little useful information. None of the light segments recovered from the annunciator panel exhibited evidence of being illuminated at impact. 1.12.3 Flight Control System Most of the sections of the flight controls were recovered, with the exception of some fragments of casting and tubing in the cyclic control installation. All fractures were examined and, although severe impact damage was evident throughout, there was no evidence found of pre- impact failure. 1.12.4 Power Plant The engine (Allison 250-C20B, S/N CAE-833728) was examined at a Transport Canada (TC) certified engine overhaul facility by TSB staff. The compressor had foreign object damage (FOD) to the first-stage through to the third- stage blades. There was considerable machining of the abradable material of the axial compressor housing. The impeller had machined into the aluminum case. The turbine section had aluminum particles fused to the blades and shrouds. There was some rub evidence on the fourth turbine wheel. The above evidence indicates that the engine was operating and capable of producing power at impact. 1.12.5 Transmission The transmission was being operated on a TC-approved time extension to 1,600 hours from the normal 1,500 hours; it had 1,584 hours at the time of the occurrence. When examined, the input and output shafts turned normally, and all internal gears and bearings were in excellent condition and displayed no signs of wear or lack of lubrication. There was no evidence of an unbalanced condition on the transmission mounting points. 1.12.6 Tail Rotor Gearbox The tail rotor input and output shafts, when examined, turned freely. The input and output splines were undamaged. There was some evidence of wear on the gears and bearings, but this wear was determined to be within serviceable limits. 1.12.7 Hydraulic Servo Actuators The three hydraulic servo actuators were examined at a TC-certified overhaul facility. Both cyclic servo actuators were unremarkable; however, 18 fragments of ferrous material were found in the collective servo actuator. These fragments and the collective servo actuator were further examined at the TSB Engineering Branch Laboratory. This component had been manufactured in 1979 and, at the time of the occurrence, had accumulated a total of 6,000 hours in service. It was concluded that the particles found in the servo actuator were likely machine turnings from some previous manufacturing process. They had likely been carried over within the interior passageways of the rod assembly, only to be released some time later in the operating life of the servo. The possibility that the fragments had somehow interfered with the operation of the collective control was considered. The component had been installed in the accident aircraft since 1989 and there were no entries in the aircraft technical logs indicating any prior collective control difficulty. The examination found evidence that at least three particles had been in contact with the servo spool valve during service (LP 80/94). Tests and analysis concluded that, given the physical characteristics of the contaminant particles found and the design and construction of the servo actuator and the collective control system, it is most probable that any interference with spool valve movement that might occur could be overcome by a collective control stick input force well within the capability of the pilot. 1.13 Medical Information There was no evidence that incapacitation or physiological factors affected the pilot's performance. 1.14 Fire 1.15 Survival Aspects It was determined that all the occupants were wearing their seat-belts prior to impact. The seat- belts had all failed at their attachment points. The accident was considered to be non-survivable due to the magnitude of the deceleration forces. 1.16 Other Operational Factors 1.16.1 Visual Flight Rules The flight was to be conducted in uncontrolled airspace and in accordance with the weather minima for visual flight rules (VFR). These minima are detailed in Air Navigation Order (ANO) Series V, No. 3. This ANO specifies that, in uncontrolled airspace, a helicopter may be operated below 700 feet vertically from ground or water provided that the flight visibility is not less than 1/2 mile. In addition, the ANO specifies that, when the helicopter is operated in reduced visibilities, it must be operated at such a reduced airspeed as will give the pilot-in-command adequate opportunity to see other air traffic or obstructions in time to avoid a collision. According to TC Regulatory Compliance records, there has been no enforcement action taken by TC Pacific Region against any pilot for violations of this ANO during the past ten years. Regulations provide for flights in lower visibilities only under specific circumstances, including flights necessary for the saving of human lives, such as the previously mentioned flight by the search helicopter. 1.16.2 Cloud Breaking Procedure Using Rising Terrain Information gathered during the course of the investigation revealed that the technique used by the occurrence pilot to climb above a cloud or low fog layer is widely known in the Canadian commercial helicopter industry. The procedure essentially requires that the pilot maintain visual contact with the rising terrain while flying at a reduced airspeed. This airspeed, depending on the terrain and/or weather conditions, may be as slow as a walking pace. The manoeuvre often requires that the helicopter be operated within the helicopter's critical height/velocity envelope until the helicopter is above the cloud or fog layer. While performing this procedure, it is essential that the pilot not lose his visual reference with the ground and that the manoeuvre not exceed the performance limitations of the helicopter. It is known that the occurrence pilot had used this technique the day before, had used it that morning to perform his weather check, and intended to use it again later that day on a non-revenue flight planned for after the accident flight. Company management stated that they were not aware that the pilot used this procedure and that pressing the weather was actively discouraged. When queried, various other experienced helicopter pilots stated that they were aware of the cloud-breaking procedure used by the occurrence pilot. The actual frequency of use of this practice by the occurrence pilot and by the helicopter pilot community at large could not be determined. 1.16.3 Translational Speed The use of the above-mentioned technique as a fog- or cloud-breaking procedure often requires that the helicopter be flown at speeds below translational speed (approximately 10 to 15 knots). When the helicopter is operated below this speed, in a hover for example, the helicopter requires considerably more power than it does in cruising flight. While in a hover, much of the rotor's energy is used to climb through an already moving column of air dispelled downward by the rotor. In forward flight, the air ahead of the rotor is not disturbed into previous motion and, as a result, the rotor reacts on more stable air, and the rotor's energy is used more efficiently and provides more lift. 1.16.4 Whiteout Considerations The TC Aeronautical Information Publication (AIP) describes whiteout as an atmospheric optical phenomenon in which the observer appears to be engulfed in a uniformly white glow. Neither shadows, horizon, nor clouds are discernible; sense of depth and orientation is lost; only very dark, nearby objects can be seen. Whiteout occurs over an unbroken snow cover and beneath a uniformly overcast sky. Fog, falling snow, and blowing snow may also exacerbate and/or cause whiteout conditions. The AIP recommends that pilots avoid such conditions, unless they have suitable aircraft instruments and they are sufficiently experienced. Interviews were conducted with a number of individuals who were either involved with the search efforts, witnessed the aircraft depart, or had heard the helicopter while in flight. All reported that the visibility was reduced in fog to distances of a few hundred feet. Those involved in the ground search efforts reported that local area secondary roads were snow covered and offered little contrast with the surrounding terrain, and that trees in the area of Mount Harry Davis were covered with snow and hoar frost. A number of the interviewees described the circumstances as conducive to whiteout conditions. 1.16.5 Spatial Disorientation Spatial disorientation is a pilot's inability to sense correctly the position, motion, or attitude of his aircraft or himself with respect to a point in space, usually the earth's surface. With good external visual references, maintaining orientation in flight normally presents little difficulty. When external visual cues are lost, however, the pilot must rely on the aircraft's instrumentation to provide him with the reliable and relevant information required to keep him oriented and to maintain control of his aircraft. In such a situation, the pilot must be capable of suppressing conflicting sensory perceptions with respect to horizontal and gravitational references. While there is no guaranteed method, the successful suppression of this erroneous sensory information is directly related to training, time, and experience. Pilots inexperienced with instrument flying or pilots with little current instrument time are particularly susceptible to spatial disorientation when they are unexpectedly confronted with no external visual attitude references. 1.16.6 Risk Assessment When a pilot successfully performs a work-related activity that involves risks, his attitude to or perception of the risks often changes. As he becomes more accustomed to and successful at performing hazardous tasks, he comes to believe that nothing will happen to him. He can diminish the perception of the risks and even begin to feel that these activities are not hazardous. The feeling of security and self-confidence generated by this attitude encourages the person to repeat the risky activity. The more often he completes the task without adverse consequences, the more his feeling of security seems justified. And, as he is encouraged by this sense of invulnerability, the more he reduces his margin of safety and takes higher additional risks. This belief will be reinforced if the pilot observes that others are performing the same manoeuvre; consequently, the procedure becomes the norm. The unfortunate irony is that, as the perception of risk decreases, the chance of an accident increases.